1. Field of the Invention
The present invention generally relates to the operation, maintenance and servicing of machines which include hydraulic systems and, more particularly, to the connection and disconnection of hydraulic fluid conveying lines with improved safety and reduced risk of loss of hydraulic fluid.
2. Description of the Prior Art
The industrial age has been characterized by the construction and utilization of machines which provide forces beyond those which can be produced practically by one or more persons to perform work of a nature or at a rate previously far beyond human capacity. Such machines characteristically include one or more sources of power and some arrangement to transfer such power from each such source to the location in or on the machine where power is required. Hydraulic systems have become a well-known and well understood arrangement for transferring power from the power source to an arbitrary location which is often preferred, despite is relative complexity, since it offers the advantages of providing potentially precise remote control, efficient transfer of large amounts of power and freedom from constraints imposed by the geometry of the machine, which may need to be varied as the machine is used.
Therefore, hydraulic systems have been used in many applications where the machines are mobile and/or where relatively large forces may be required to provide controlled relative motion of parts of the machine. Well-recognized applications include power steering on automobiles and mechanisms for moving materials relative to the machine, such as earth-moving equipment, large snow plows, mobile cranes and the like.
It is also a common requirement, for economy, ease of maintenance or storage and the like, to provide the capacity to reconfigure the machine at will by providing folding or telescoping portions or removal of large portions of the machine such as for maintenance or seasonal storage or to provide for multiple uses of a single power source in a basic machine having a variety of interchangeable attachment mechanisms. To accommodate such arrangements and mechanisms, it is often convenient or, in some cases, necessary, to provide for disconnection of hydraulic fluid-carrying lines with convenient mechanisms such as a so-called quick-connect coupler (sometimes also referred to as a quick-disconnect coupler or simply xe2x80x9ccouplerxe2x80x9d when the context is evident to identify the type of coupler as being of this type). These arrangements are often provided as a pair of mating fittings which can be securely attached to each other or separated by hand, ideally without the use of tools, and requiring very little force to be manually applied.
The mechanical advantage necessary to achieve such a function is generally provided by retractable metal spheres similar to ball bearings which engage a generally tapered groove in a mating part of the coupler and are held in place by a movable ring which can allow or prevent retraction of the spheres. This ring is generally spring loaded to return it to a position where retraction of the spheres is prevented when the ring is not actively moved from that position. Thus, the spheres are forced into the non-retracted or extended position when the ring is released to engage the groove and to maintain the respective parts of the coupler securely affixed together. The tapering of the groove also provides compression between the mating parts of the coupler to avoid leakage and to resist internal pressure.
Unfortunately, improper seating of the spheres in the groove to form a secure connection of the mating parts may not be fully evident from the appearance of the coupler when a connection is made. If the parts of the coupler are not properly seated together and fully engaged, the coupler may become disconnected when pressure is applied, particularly if a non-axial force is also present and sufficiently coincides with the location of improperly constrained spheres. Any fluid flow, static pressure or associated mechanical arrangements such as check valves which are manipulated as coupler parts are joined together may also increase the difficulty of achieving proper seating together of the coupler parts.
Further, such a coupler, itself, does not usually have any arrangement to prevent flow from the fluid-carrying system or ingress of contaminants into it when the coupler is disconnected. Therefore, when such a coupler is used in a system carrying a particular fluid, such as hydraulic fluid, a check valve is usually employed adjacent to the coupler or integrally formed therewith to prevent loss of fluid and/or contamination. Such a provision is particularly necessary in, for example, hydraulic systems in which the fluid, to be sufficiently non-compressible and to posses other necessary properties, cannot be made non-toxic.
Unfortunately, such check valves can also allow the hydraulic system to become pressurized while a hydraulic line or conduit is disconnected. Such pressurization can occur through operation of the machine with the line disconnected or even through environmental circumstances such as an increase in ambient temperature causing expansion of the hydraulic fluid. If a hydraulic line is connected while the system is pressurized against the check valve, the system will not be functional since the check valve will continue to resist fluid flow unless and until the pressure is overcome.
In this regard, it should be noted that most hydraulic systems use recirculating flow of fluid and two hydraulic lines are generally used to support fluid flow in opposite directions into or out of the machine and part, respectively. Check valves are generally used on both sides of each coupler to avoid both fluid loss and contamination. Fluid flow into the machine or part tends to counteract any existing pressure in the line and thus does not present a problem. However, fluid pressure corresponding to the outward direction of flow from the machine or part will maintain the check valve in a closed position, preventing flow during operation of the machine. Accordingly operation of the machine cannot provide for opening of the check valve since operation provides pressure in the same direction as any existing pressure in the hydraulic system.
Therefore, it is conventional to provide a mechanical arrangement to hold check valves open on both sides of the coupler when the coupler parts are connected. However, if the line is pressurized, any such mechanical arrangement will prevent the coupler parts from seating together to make a connection and thus pressure against the check valve must be released whenever a connection of a disconnectable line is made.
At the present state of the art, the only technique available and consistent with the operation of a quick-connect coupler is to unseat the check valve manually; generally by using a punch which is placed against the moveable portion of the valve and struck with an implement such as a hammer. Neither of these tools are generally used in other operations on the machine generally performed during operations requiring the connection of hydraulic lines; thus presenting a substantial inconvenience. Also, while the check valve is generally made of steel in a ball-shaped or pointed configuration, the punch or other tool must be a specially made of a softer material such as brass to avoid or at least minimize damage thereto resulting in a relatively non-durable tool. For this reason, use of a tool of softer material often results in particles of the punch being removed and deposited within the valve or coupler part from which they can become dislodged, circulate through the system and cause damage to pumps, control valves and hydraulic actuators or prevent proper functioning of the check valves. Valves of pointed configuration tend to increase such chipping of the punch. In practice, however, maintenance personnel will tend to use any tool available, such as an ordinary screwdriver, which is much more likely to damage the check valve and produce particles or chips of harder and even more potentially damaging material.
Perhaps more importantly, such an arrangement and technique does not provide for avoidance of loss of (usually toxic) fluid from the system as it is depressurized. There is a safety concern, as well, since hydraulic systems can contain pressures sufficient to drive the hydraulic fluid through the skin of the person performing the depressurization operation, much in the nature of an inoculation. The likelihood of such an occurrence is increased by the common practice of wrapping the connection (and punch) in a rag which is manually held in place while the punch is struck in an effort to avoid or reduce release of the fluid into the environment.
Specialized tools are known for depressurizing some types of fluid handling systems while collecting fluid therefrom but which are not readily applicable to systems such as hydraulic systems which may contain much higher pressures, denser fluid and/or are generally depressurized only for service and are provided with a standardized fitting for such purpose. For example, U.S. Pat. No. 4,921,013 to Spalink et al. is directed to a tool for axially moving a part of a self-sealing valve in a refrigeration system such as an automotive air conditioner, heat pump or the like. When the stool is attached to the valve using a quick coupler and the check valve is opened by the movement of a threaded valve actuator, refrigerant (generally in a vapor phase at relatively low pressure) is released into the body of the tool and, as a further valve within the tool is opened, the refrigerant flows out of a fluid port formed in the side of the tool for collection.
However, such a design would present several problems if applied to other types of fluid handling systems such as hydraulic systems. If used to depressurize a system using fluid in a denser, liquid phase and at higher pressure, the acceleration of fluid during redirection to a lateral port can cause substantial lateral forces that may unseat the quick connect coupler; causing the tool to become detached from the system and loss of fluid into the environment and possible injury to the user. More importantly from the standpoint of economy and convenience, it is common practice to provide a valve for depressurizing of the system in a standardized form and size since depressurization is usually performed only for relatively infrequent servicing the system. Thus a standard tool can be used on virtually all systems of a given type and the relative convenience of location and expense of providing an additional fitting to allow depressurization is of relatively low importance.
However, in the case of attachment of hydraulic lines to machines or the like, many different sizes of lines and couplers as well as couplers made by different manufacturers (which may not be compatible) may be encountered and it is highly inconvenient to depressurize a line at any location other than the coupler at which an attachment of a connecting line is to be made. Therefore, a different specialized, complex and expensive tool would be required for each size/diameter of line and each manufacturer of coupler fittings which may be encountered which would, itself present substantial cost and inconvenience. By the same token, the lateral port essentially characterizes the specialization of such tools and a commercially available coupler for which compatibility is expected cannot be modified to form a part of the specialized tool since the region in which a lateral port would be made is thin and presents a convex surface that can be drilled only with difficulty and weakening of the fitting and cannot generally be tapped to form the lateral port by a threaded joint. Accordingly, there has been no reasonable alternative to depressurization of hydraulic lines and the like using a punch or other available tool notwithstanding the drawbacks and dangers thereof as discussed above.
It is therefore an object of the present invention to provide an easily employed mechanism for depressurizing a hydraulic system safely and without loss of fluid into the environment and without damage to the hydraulic system.
It is another object of the invention to allow use of commercially available couplers for attachment of a depressurizing arrangement to a pressurized system such as a hydraulic line.
In order to accomplish these and other objects of the invention, an apparatus for releasing pressure from a conduit having a check valve in the proximity of a connection fitting is provided comprising a body adapted to removably engage a mating fitting for said connection fitting and an internal axial bore, and a pressure release mechanism engaging a portion of the inner axial bore with a screw threaded portion of an outer surface and having an axially extending fluid passage therein and a portion for axially engaging the check valve.
In accordance with another aspect of the invention, a method is provided for depressurizing a conduit having a check valve therein including steps of connecting an adapter to a portion of a connection fitting for connection to a portion of another connection fitting, applying forces to the check valve along an axis of the adapter, and releasing fluid from the check valve to flow through the adapter in a direction substantially axial of the adapter.